Resists for use in microfabrication by lithography are prepared from various materials. For example, a resist for use in production of semiconductors is prepared by polymerizing one or more kinds of monomers and adding an additive, acid generating agent, solvent or the like to the polymerized product. In these resists, their contamination by impurities need to be reduced as much as possible depending on the purpose. Therefore, in the production of a monomer for resists, too, it is preferable to reduce the formation of by-product.
Commonly employed processes for synthesizing esters include, for example, addition reaction of alkene and (meth)acrylic acid performed in the presence of acid catalyst; dehydration (in the presence of condensation agent or acid catalyst) of alcohol and (meth)acrylic acid; transesterification between alcohol and ester; and esterification by acid chloride.
Monomers for resists each having an alicyclic structure are three-dimensionally bulky and subject to decomposition by acid. Therefore, generally it is difficult to synthesize such monomers by addition reaction, dehydration or transesterification in the presence of acid catalyst. As a result, usually such monomers are frequently synthesized by esterification by acid chloride, as described in JPN. J. Appl. Phys. 1996, 35(4B) L 528–530. Ester synthesis by transesterification using a titanium- or tin-containing compound is also well known.
In the synthesis of monomers for resists, however, since alcohol itself used as a starting material is bulky, when conducting transesterification by the well known processes as above, the reaction is often retarded significantly or often does not progress at all due to the inactivation of catalyst and the like.
In addition, since resists prepared by chemical syntheses as described above are contaminated much by by-products or catalyst added, their purification requires great labor. In such context, an ester synthesizing process for producing monomers for resists has been desired which uses no acid catalysts, is carried out under mild conditions and makes product purification easier.
On the other hand, esterification or transesterification by enzymes is widely known. However, since enzymatic reactions are highly substrate-selective and site-selective, generally it is difficult to use enzymes in transesterification for producing bulky monomers, and there have been no examples in which enzymes are applied to special monomers of high bulk, such as monomers for resists.